True, you did say they were all going to be "very, very good" but you understand my point right? The more time you spend polishing, playtesting and tweaking a game the better it can be. Therefore if you try writing a bunch of games you just wont have time to give them all the most amount of polish, right?
Then again i might be working with the assumtion that you have limited free-time to work on gamebooks. I work 12 hour days so i dont have a lot of time in the evenings for writing gamebooks, so it probably just makes more sense in my situation to focus on one or two games instead of writing a bunch like you.